Magnetization dependent tunneling conductance of ferromagnetic barriers

Zhe Wang,Enrico Giannini,Marco Gibertini,Takashi Taniguchi,Nicolas Ubrig,Alberto F Morpurgo,Ignacio Gutiérrez-Lezama,Kenji Watanabe,Dumitru Dumcenco

doi:10.1038/s41467-021-26973-7

Abstract

Recent experiments on van der Waals antiferromagnets have shown that measuring the temperature (T) and magnetic field (H) dependence of the conductance allows their magnetic phase diagram to be mapped. Similarly, experiments on ferromagnetic CrBr3 barriers enabled the Curie temperature to be determined at H = 0, but a precise interpretation of the magnetoconductance data at H ≠ 0 is conceptually more complex, because at finite H there is no well-defined phase boundary. Here we perform systematic transport measurements on CrBr3 barriers and show that the tunneling magnetoconductance depends on H and T exclusively through the magnetization M(H, T) over the entire temperature range investigated. The phenomenon is reproduced by the spin-dependent Fowler–Nordheim model for tunneling, and is a direct manifestation of the spin splitting of the CrBr3 conduction band. Our analysis unveils a new approach to probe quantitatively different properties of atomically thin ferromagnetic insulators related to their magnetization by performing simple conductance measurements.

Highlights

Recent experiments on van der Waals antiferromagnets have shown that measuring the temperature (T) and magnetic field (H) dependence of the conductance allows their magnetic phase diagram to be mapped
The net result is an sharp change in the measured conductance that can be traced to identify the phase boundary. These conclusions have been drawn from experiments on different antiferromagnetic insulators (CrI37–10, CrCl311–14 and MnPS316) that exhibit well-defined phase boundaries in the H − T plane associated to either spin-flip or spin-flop transitions, across which the symmetry of the magnetic state changes
There is no true continuous phase boundary separating the paramagnetic and ferromagnetic states in the H − T plane[19], the Curie temperature TC is an isolated point, and what precise information can be extracted from magnetotransport measurements is less obvious

Summary

Introduction

Recent experiments on van der Waals antiferromagnets have shown that measuring the temperature (T) and magnetic field (H) dependence of the conductance allows their magnetic phase diagram to be mapped. Experiments on ferromagnetic CrBr3 barriers enabled the Curie temperature to be determined at H = 0, but a precise interpretation of the magnetoconductance data at H ≠ 0 is conceptually more complex, because at finite H there is no well-defined phase boundary. The net result is an sharp change in the measured conductance that can be traced to identify the phase boundary These conclusions have been drawn from experiments on different antiferromagnetic insulators (CrI37–10, CrCl311–14 and MnPS316) that exhibit well-defined phase boundaries in the H − T plane (i.e., in their phase diagram) associated to either spin-flip or spin-flop transitions, across which the symmetry of the magnetic state changes. There is no true continuous phase boundary separating the paramagnetic and ferromagnetic states in the H − T plane (since the two states cannot be differentiated in terms of their symmetry)[19], the Curie temperature TC is an isolated point, and what precise information can be extracted from magnetotransport measurements is less obvious

Methods

Results

Conclusion